According to unnamed sources, Foley said Windows Blue has hit the halfway point of development, and the last milestone build will be M2. Because of the rapid pace that Windows Blue is being developed, there is no estimated timetable for when development and testing will be complete.

"It's hard to know what will come next, given Windows Blue is the first Windows release to be on an accelerated schedule," wrote Foley. "Will Microsoft deliver a developer preview of Blue? A consumer preview? Or just go straight from internal milestone builds to final? (I'm thinking it's likely to be the last option, if the Windows team sticks to an earlier leaked target ship date of August 2013.)"

A rumored screenshot of Windows Blue also surfaced online today, which Foley said brings some validity that her sources were correct on the current status of Windows Blue.

While Microsoft has refused to comment on the project, Windows Blue is rumored to be a comprehensive update for not only Windows 8, but for multiple Microsoft products and services, including Windows Phone 8, Hotmail, SkyDrive, and Windows Server 2012, to name a few.

Late last week more information surfaced on the project in a Microsoft software development engineer job posting:

"We're looking for an excellent, experienced SDET to join the Core Experience team in Windows Sustained Engineering (WinSE). The Core Experience features are the centerpiece of the new Windows UI, representing most of what customers touch and see in the OS, including: the start screen; application lifecycle; windowing; and personalization. Windows Blue promises to build and improve upon these aspects of the OS, enhancing ease of use and the overall user experience on devices and PCs worldwide."

Windows Blue and its mobile counterpart, codenamed "Windows Phone Blue" are rumored to be the first of multiple annual updates for Microsoft's current generation of products.